Creating a scientific basis for an integrated evaluation of soil-borne GHG emissions in Norwegian agriculture

Agroecosystems contribute to global warming by direct and indirect emissions of the greenhouse gases CO2, CH4 and N2O. Cultivated soils are either net sinks or sources for CO2 and strong sources of N2O. Thus, cultivated soils indisputably contribute to th e total GHG budget of food production. However, the magnitude of soil related emissions is highly uncertain owing to regional differences in soil conditions, climatic factors, management regimes and cultivation history. We therefore propose a 3-year empir ical project to provide a minimum of empirical data for evaluating N2O and CO2 emission factors for the most relevant Norwegian production systems. Whole-year-round measurements of N2O emission will provide benchmark data sets for two dominating agronomic /climatic systems: grassland/dairy farming in the west (wet marine climate) and grain cropping in the east (dry continental). Specific variations in cultivation practices and local soil/climate conditions will be addressed by additional measurements. In p arallel, we will explore selected soil cultivation strategies (slow-release liming, biochar incorporation and inclusion of perennial leys) with respect to their GHG mitigation potential under Norwegian conditions, both in field and laboratory experiments. The project builds on field observations, plot experiments, laboratory screening of soil processes, dynamic modelling and an overall integration of findings in a state-of-the-art climate gas calculator (Norwegian HOLOS). Ultimately, a scientifically soun d approach to soil-borne GHG emissions from Norwegian agriculture will facilitate accounting methods that aim at analysing the life cycle of Norwegian food production in a wider societal context.